ElectroSpray Deposition system as sample preparation for NP analysis by EM & HRMA as on line analysis technique for the smallest NP range

Transcription

1 ElectroSpray Deposition system as sample preparation for NP analysis by EM & HRMA as on line analysis technique for the smallest NP range Industrial workshop. Frankfurt 24 October 2017 Silvia López Vidal RAMEM NanoDefine is funded by the European Community's Seventh Framework Programme under Grant Agreement

2 Electrospray Deposition System as Sample Preparation Technique for Nanoparticle Analysis by Electron Microscopy Iñaki Mugica, Silvia Lopez-Vidal, Pavla Dohányosová IONER. RAMEM s brand. C/ Verano, 9. Torrejón de Ardoz. Madrid. Johannes Mielke, Vasile-Dan Hodoroaba Federal Institute for Materials Research and Testing (BAM), Berlin, Germany. Philipp Müller BASF SE, Material Physics Research, Ludwigshafen, Germany Cristina Gutierrez-Cañas University of the Basque Country (UPV/EHU)

3 1. Introduction 2. Motivation and goal 3. Electrospray fundaments 4. Experimental methods and equipment 5. Results 6. Conclusions

4 Motivation and goal Sample preparation method for nanoparticle characterization by EM. Challenge: Particle agglomeration Non homogeneous deposition» representability of the sample Solution: Miniminization of the agglomeration by charging the Nanoparticles ES

5 ElectroSpray fundamentals Conductor liquid Taylor Cone Cone-jet Cloud of micro-drops Electric field ES conditions Charged NP dry residues Charge repulsion + Evaporation Evaporation

6 ElectroSpray fundamentals: Droplet size (*) Primary droplet size: d = G(ε)(Q ε ε0 /ke)^(1/3) Q flow rate of the liquid sample through the capillary. Different id available, therefore different flowrates achievable. ε and ε0 are dielectric constant of the sample and vacuum, respectively. G(ε) is a function of order unity. ke : electric conductivity of the sample General rule: Higher ke, smaller droplets For high ke, the droplets are highly charged and can be close to the Rayleight limit (calculator: (*) From: Aerosol measurement : principles, techniques, and applications. P. Kulkarni; P.A. Baron; K. Willeke. Hoboken, N.J. : Wiley, 2011

7 Experimental methods and equipment ES-DEPO Prototype

8 Experimental methods and equipment Sample preparation Deposition EM Image treatment

9 Results. Studied NP suspensions. Materials Preparation Stabilizer Particle size [nm] Particle Shape Au NPs Suspension as provided Unknown 20 Spherical Au NPs Dilutied to 30% with ultra pure water Thiocyanate 2 Spherical Au NPs Dilutied to 30% with ultra pure water Citrate 5 Spherical Ag NPs Dilution 1/200 with ultra pure water Polyacrilic acid 6 Spherical Bi-modal SiO2 (ERM FD102) Suspension as provided Unknown 18.2, 84.0 Spherical Mono-modal SiO2 (ERM FD304) Dilution 1/100 with ultra pure water Unknown 28 Spherical PSL tri-modal Dilution Dilution 1/100 with ultra pure water Unknown 46, 100, 350 Spherical BaSO4 (f) Aqueous suspension SHMP 250 BaSO4 (uf) Aqueous suspension SHMP 30 Roughly spherical Roughly spherical Kaolin Aqueous suspension None 37 (thickness) Platelet

10 Results. Studied NP suspensions. ESI vs drop-on-grid Bimodal SiO2-ERM FD102

11 Results. Influence of the jet. The region of deposition was observed to be about 1 cm in diameter The size distribution at the outer regions of the TEM grid (regions 1 4) seems to be different from the one in the centre (5 and 6). The relative number of large particles in the centre of the grid is higher than at the border.

12 Results. Drop border effect. Stable cone-jet mode Unstable cone-jet mode

13 Results: High Voltage polarity of the electrospray.

14 Conclusions Electrospray deposition of particle suspensions on a EM grid is a very promising option for achieving homogeneous particle distributions and minimizing agglomeration effects. No dedicated commercial instruments are available for the NP suspension sample preparation for EM grids, therefore, it is an interesting industrial opportunity. The results obtained depend greatly on the ability of the user to work in the stable cone-jet mode of the electrospray. For this reason it is important to obtain all the significant information about the suspension for determining its operation conditions. Another key aspect is minimize the size of generated droplets and to ensure the total evaporation of the solvent in order to minimizing undesirable effects.

15 Conclusions With polydisperse nanoparticules it has been observed that the relative number of large particles in the center of the grid is higher than at the border, which can be explained by higher inertia, and therefore lower charge-to-mass ratio, of larger particles compared with smaller ones. This effect can also be used to obtain a radial distribution of sizes. We have not found decisive evidences of the effect of the polarity of the high voltage source in the agglomeration phenomena because there are differences in the electrospray working mode.

16 Current and future work Apply the ES-DEPO for aerosolization of nanoparticles for toxicity studies. Especially in the smallest range. Go deeper into studies about the negative ES. Heating the aerosol in order to ensure the evaporation. Optimise the ES-DEPO for surface coating and other similar applications. Willing to collaborate in H2020 projects for further applications.

17 HRMS: High Resolution Mobility Spectrometer Objective: Development of an instrument to extend the size distribution analysis to the smallest rage of the nanoscale: Nanoparticles smaller than 5nm. Technical challenges: High mobility: high losses, high diffusion; real samples: Sensitivity Proposal: Use a parallel plate HRMS based on DMA, an aerosol technique: Stages: Charging stage: ES Classification stage: DMA Detection stage: Electric Electrometer

18 HRMS: Prototype Particle generator + charger Classifier Detector Sheath gas circuit Electronics SW

19 HRMS: Characterization with mobility standards Due to the lack of true size standards molecular standards of sharply defined mobility are used : Tetra heptyl ammonium ions D= 1.47nm, Z 0 (A + ) = 0,89cm 3 /(Vs) D= 1.70nm, Z 0 =0,63 cm 3 /(Vs) Tetra-dodecyl ammonium ions D= 2.57nm, Z 0 =0,57 cm 3 /(Vs) (Ude and de la Mora (2005)) Name, date and location of the event

20 HRMS: Resolution Resolving power RP = V(x c )/FWHH FWHH = σ 2 2 ln (2) Tetra heptyl ammonium ions d em (A + ) = 1,47 nm Tetra-dodecyl ammonium ions d em (A + ) = 1,7 nm d em (A 2+ (AB) 2 ) = 2,57 nm Name, date and location of the event

21 HRMS: Quantitative results

22 HRMS: NP first experiments Brussels, Sept 2017

23 This project has received funding from the European Union s Seventh Programme for research, technological development and demonstration under grant agreement No